Chuanbin Mao

Viral assembly of oriented quantum dot nanowires

The highly organized structure of M13 bacteriophage was used as an evolved biological template for the nucleation and orientation of semiconductor nanowires. To create this organized template, peptides were selected by using a pIII phage display library for their ability to nucleate ZnS or CdS nanocrystals. The successful peptides were expressed as pVIII fusion proteins into the crystalline capsid of the virus. The engineered viruses were exposed to semiconductor precursor solutions, and the resultant nanocrystals that were templated along the viruses to form nanowires were extensively characterized by using high-resolution analytical electron microscopy and photoluminescence. ZnS nanocrystals were well crystallized on the viral capsid in a hexagonal wurtzite or a cubic zinc blende structure, depending on the peptide expressed on the viral capsid. Electron diffraction patterns showed single-crystal type behavior from a polynanocrystalline area of the nanowire formed, suggesting that the nanocrystals on the virus were preferentially oriented with their [001] perpendicular to the viral surface. Peptides that specifically directed CdS nanocrystal growth were also engineered into the viral capsid to create wurtzite CdS virus-based nanowires. Lastly, heterostructured nucleation was achieved with a dual-peptide virus engineered to express two distinct peptides within the same viral capsid. This work represents a genetically controlled biological synthesis route to a semiconductor nanoscale heterostructure.

Upconversion nanoparticles: synthesis, surface modification and biological applications

UNLABELLED New generation fluorophores, also termed upconversion nanoparticles (UCNPs), have the ability to convert near infrared radiations with lower energy into visible radiations with higher energy via a nonlinear optical process. Recently, these UCNPs have evolved as alternative fluorescent labels to traditional fluorophores, showing great potential for imaging and biodetection assays in both in vitro and in vivo applications. UCNPs exhibit unique luminescent properties, including high penetration depth into tissues, low background signals, large Stokes shifts, sharp emission bands, and high resistance to photobleaching, making UCNPs an attractive alternative source for overcoming current limitations in traditional fluorescent probes. In this article, we discuss the recent progress in the synthesis and surface modification of rare-earth doped UCNPs with a specific focus on their biological applications. FROM THE CLINICAL EDITOR Upconversion nanoparticles - a new generation of fluorophores - convert near infrared radiations into visible radiations via a nonlinear optical process. These UCNPs have evolved as alternative fluorescent labels with great potential for imaging and biodetection assays in both in vitro and in vivo applications.

Virus-based chemical and biological sensing

Viruses have recently proven useful for the detection of target analytes such as explosives, proteins, bacteria, viruses, spores, and toxins with high selectivity and sensitivity. Bacteriophages (often shortened to phages), viruses that specifically infect bacteria, are currently the most studied viruses, mainly because target-specific nonlytic phages (and the peptides and proteins carried by them) can be identified by using the well-established phage display technique, and lytic phages can specifically break bacteria to release cell-specific marker molecules such as enzymes that can be assayed. In addition, phages have good chemical and thermal stability, and can be conjugated with nanomaterials and immobilized on a transducer surface in an analytical device. This Review focuses on progress made in the use of phages in chemical and biological sensors in combination with traditional analytical techniques. Recent progress in the use of virus-nanomaterial composites and other viruses in sensing applications is also highlighted.

Preparation and Characterization of Fe3O4/CdTe Magnetic/Fluorescent Nanocomposites and Their Applications in Immuno-Labeling and Fluorescent Imaging of Cancer Cells

The synthesis of a new kind of magnetic, fluorescent multifunctional nanoparticles (approximately 30 nm in diameter) was demonstrated, where multiple fluorescent CdTe quantum dots (QDs) are covalently linked to and assembled around individual silica-coated superparamagnetic Fe(3)O(4) nanoparticles and active carboxylic groups are presented on the surface for easy bioconjugation with biomolecules. The Fe(3)O(4) nanoparticles were first functionalized with thiol groups, followed by chemical conjugation with multiple thioglycolic acid modified CdTe QDs to form water-soluble Fe(3)O(4)/CdTe magnetic/fluorescent nanocomposites. X-ray diffraction, infrared spectroscopy, transmission electron microscopy, absorption and fluorescence spectroscopy, and magnetometry were applied to fully characterize the multifunctional nanocomposites. The nanocomposites were found to exhibit magnetic and fluorescent properties favorable for their applications in magnetic separation and guiding as well as fluorescent imaging. The carboxyl groups on the nanocomposite surface were proved to be chemically active and readily available for further bioconjugation with biomolecules such as bovine serum albumin and antibodies, enabling the applications of the nanocomposites for specific recognition of biological targets. The Fe(3)O(4)/CdTe magnetic/fluorescent nanocomposites conjugated with anti-CEACAM8 antibody were successfully employed for immuno-labeling and fluorescent imaging of HeLa cells.

Multifunctional nanocomposites of superparamagnetic (Fe3O4) and NIR-responsive rare earth-doped up-conversion fluorescent (NaYF4 : Yb,Er) nanoparticles and their applications in biolabeling and fluorescent imaging of cancer cells

A new kind of magnetic/luminescent multifunctional nanoparticles was synthesized by covalently linking multiple carboxyl-functionalized superparamagnetic Fe(3)O(4) nanoparticles and individual amino-functionalized silica-coated fluorescent NaYF(4) : Yb,Er up-conversion nanoparticles (UCNPs). The resultant nanocomposites bear active carboxylic and amino groups on the surface that were proved to be chemically active and useful for further facile bioconjugation with biomolecules. The UCNPs in the nanocomposite particles can emit visible light in response to the irradiation by near infrared (NIR) light, enabling the application of the nanocomposites in bioimaging. X-Ray diffraction, infrared spectroscopy, transmission electron microscopy, luminescence spectroscopy, and magnetometry were applied to characterize the multifunctional nanocomposites. The nanocomposites exhibited good superparamagnetic and excellent green up-conversion photoluminescent properties that can be exploited in magnetic separation and guiding as well as bioimaging. Due to the presence of active functional groups on the nanocomposite surface, the Fe(3)O(4)/NaYF(4) : Yb,Er magnetic/luminescent nanocomposites were successfully conjugated with a protein called transferrin, which specifically recognizes the transferrin receptors overexpressed on HeLa cells, and can be employed for biolabeling and fluorescent imaging of HeLa cells. Because NIR light can penetrate biological samples with good depth without damaging them and can avoid autofluorescence from them, the presence of both NIR-responsive UCNPs and superparamagnetic nanoparticles in the nanocomposite particles will enable the practical application of the nanocomposites in bioimaging and separation.

Phage nanofibers induce vascularized osteogenesis in 3D printed bone scaffolds

A virus-activated matrix is developed to overcome the challenge of forming vascularized bone tissue. It is generated by filling a 3D printed bioceramic scaffold with phage nanofibers displaying high-density RGD peptide. After it is seeded with mesenchymal stem cells (MSCs) and implanted into a bone defect, the phage nanofibers induce osteogenesis and angiogenesis by activating endothelialization and osteogenic differentiation of MSCs.

Controlled growth and differentiation of MSCs on grooved films assembled from monodisperse biological nanofibers with genetically tunable surface chemistries

The search for a cell-supporting scaffold with controlled topography and surface chemistry is a constant topic within tissue engineering. Here we have employed M13 phages, which are genetically modifiable biological nanofibers (∼ 880 nm long and ∼ 6.6 nm wide) non-toxic to human beings, to form films for supporting the growth of mesencymal stem cells (MSCs). Films were built from nearly parallel phage bundles separated by grooves. The bundles can guide the elongation and alignment of MSCs along themselves. Phage with peptides displayed on the surface exhibited different control over the fine morphologies and differentiation of the MSCs. When an osteogenic peptide was displayed on the surface of phage, the proliferation and differentiation of MSCs into osteoblasts were significantly accelerated. The use of the grooved phage films allows us to control the proliferation and differentiation of MSCs by simply controlling the concentrations of phages as well as the peptides displayed on the surface of the phages. This work will advance our understanding on the interaction between stem cells and proteins.

Bio-imaging, detection and analysis by using nanostructures as SERS substrates

Surface-enhanced Raman scattering (SERS) is a phenomenon that occurs on nanoscale-roughed metallic surface. The magnitude of the Raman scattering signal can be greatly enhanced when the scatterer is placed in the very close vicinity of the surface, which enables this phenomenon to be a highly sensitive analytical technique. SERS inherits the general strongpoint of conventional Raman spectroscopy and overcomes the inherently small cross section problem of a Raman scattering. It is a sensitive and nondestructive spectroscopic method for biological samples, and can be exploited either for the delivery of molecular structural information or for the detection of trace levels of analytes. Therefore, SERS has long been regarded as a powerful tool in biomedical research. Metallic nanostructure plays a key role in all the biomedical applications of SERS because the enhanced Raman signal can only be obtained on the surface of a finely divided substrate. This review focuses on progress made in the use of SERS as an analytical technique in bio-imaging, analysis and detection. Recent progress in the fabrication of SERS active nanostructures is also highlighted.

Novel microwave-assisted solvothermal synthesis of NaYF4:Yb,Er upconversion nanoparticles and their application in cancer cell imaging.

This work reports the novel microwave-assisted solvothermal synthesis and structural, topographic, spectroscopic characterization of NaYF(4):Yb,Er upconversion nanoparticles (UCNPs) as well as their application in the labeling of HeLa cells. The nanoparticles were prepared in ethylene glycol, with rare earth acetates as precursor and NH(4)F and NaCl as the fluorine and sodium sources. X-ray diffraction, transmission electron microscopy, and luminescence spectroscopy were applied to characterize the nanoparticles. Experimental results showed that the microwave-assisted solvothermal method is an effective approach to create highly crystalline, strongly luminescent UCNPs at a lower temperature (160 °C) and within a significantly shortened reaction time (only 1 h) compared to the traditional methods. The effect of fluorine source on the optical properties of UCNPs was investigated by using NH(4)F, NH(4)HF(2), NaF, and 1-butyl-3-methylimidazolium tetrafluoroborate (BmimBF(4)) as different fluorine sources; NH(4)F proved to be the best one, making the luminescent intensity increase at least 2 orders of magnitude. The UCNPs with four different colors (green, yellow, orange, and cyan) were successfully obtained. After being modified with amino groups and coupled with CEA-8 antibody, the obtained nanoparticles were successfully applied in the specific fluorescent immunolabeling and imaging of HeLa cells to further verify their function as a marker in immunolabeling.

Nanofibrous bio-inorganic hybrid structures formed through self-assembly and oriented mineralization of genetically engineered phage nanofibers.

Nanofibrous organic–inorganic hybrid structures, where inorganic nanocomponents are formed or assembled within the aligned organic nanofibrous matrix, are important materials that can find applications in electronics, photonics, catalysis, and tissue engineering.[1–11] They not only provide a means for supporting and ordering the functional inorganic materials such as nanoparticles,[4–6,8] but also can serve as building blocks to further self-assemble into higher-order structures.[5,11,12] The common approaches to the synthesis of the nanofibrous organic-inorganic hybrid structures include electrospinning,[2,4,10] polymer-templating,[3] biotemplating,[5–7,11] and directional freezing.[1] As a matter of fact, the nanofibrous organic-inorganic hybrid structures are important building blocks in natural mineralized biomaterials. One of the best examples is the mineralized collagen fibrils constituting the extracellular matrix (ECM) of bone.[13] Bone is made of cells embedded in ECM, which is hierarchically organized from proteins, including type I collagen and non-collagenous proteins (NCPs) such as bone sialoprotein (BSP), and calcium hydroxylapatite (HAP, Ca10(PO4)6(OH)2). The collagen molecules (~1.5 nm wide and 300 nm long) are self-assembled into wider (up to 200 nm wide) and longer (several µm long) fibrils in a side-to-side and head-to-tail format, which are further hierarchically self-assembled to form much wider and longer collagen fibers (up to several tens µm wide and long).[14,15] HAP is found within the gaps and grooves of the collagen fibers with its c-axis preferentially along the collagen fibers.